Lactic acid bacteria (LAB) are Gram-positive bacteria that produce lactic acid by the fermentation of glucose. Lactic acid bacteria have been widely used in various fermented food products around the world for many centuries and have been shown to exhibit various beneficial biological functions. Some lactic acid bacteria are also referred to as probiotics. According to the World Health Organization, the term “probiotics” describes live microorganisms which confer a health benefit to a host. The most frequently used species are Lactobacillus spp., Bifidobaterium spp. and Saccharomyces spp. A number of mechanisms of action have been proposed to explain the efficacy of probiotics. These mechanisms include production of antimicrobial substances, competition for gastro-intestinal colonization as well as for available nutrients, production of antimicrobial bacteriocins, immunomodulation and promotion of lactose digestion (Lu et al., 2001; D'Souza et al., 2002; Alvarez-Olmos et al., 2001).
Antibiotics have substantially decreased morbidity and mortality from bacterial infections in the 20th century. However, microorganisms are showing more and more resistance to existing antibiotics. This antibiotic resistance phenomenon is a serious threat to public health. Probiotics may act as biotherapeutic agents and help solve public health issues pertaining to multidrug resistance. Methicillin resistant Staphylococcus aureus (MRSA) is a specific strain of bacteria that shows resistance to many antibiotics including methicillin. MRSA infections are typically acquired in healthcare (nosocomial infections) and community settings. Although Staphylococcus aureus strains usually utilize three penicillin-binding proteins (PBP) in the synthesis of their cell wall, those that are resistant to methicillin (MRSA) possess a supplementary PBP, PBP2a, encoded by the mecA gene which allows cells to grow in the presence of methicillin, oxacillin and other beta-lactam antibiotics (Martins et al., 2007).
It is estimated that more than 90% of Staphylococcus aureus infections are resistant to methicillin and other antibiotics (Mathur and Singh, 2005). The lack of efficacy of various antibiotics and the increasing prevalence of MRSA has become a major public health issue and resistance of Staphylococci to methicillin is a problem of global proportions. There is a clear need for new antibacterial agents to control methicillin-resistant Staphylococcus aureus. Such agents would provide significant therapeutic value for the prevention, reduction and/or treatment of MRSA infections. The present invention seeks to meet this and other needs.
The present description refers to a number of documents, the content of which is herein incorporated by reference in their entirety.